Budget cuts mandated by the sequester will have an “insidious” impact on U.S. national security and on the ability of America’s spy agencies to do their work, Director of National Intelligence James Clapper said Tuesday.

Speaking at an annual Senate hearing intended to focus on the threats America faces around the globe, Clapper quickly named the threat to their budgets as the big threat intelligence agency leaders are struggling with at the moment.

“The topic [that] is foremost on our minds this year is, of course, sequestration,” Clapper told the Senate Intelligence Committee.

“In my considered judgment as the nation’s senior intelligence officer, sequestration jeopardizes our nation’s safety and security and this jeopardy will increase over time,” Clapper said. “Unlike more directly observable sequestration impacts like shorter hours in public parks and longer security lines at airports, the degradation to intelligence will be insidious. It will be gradual and almost invisible, unless and until of course, we have an intelligence failure.”

Clapper complained that much of the intelligence community’s funding is subject to “an even more onerous set of rules than that imposed on the Defense Department.” He said intelligence agencies are required to cut each program, project and activity by 7 percent in the current fiscal year, which amounts to a 13 percent cut because the cuts are just beginning and the fiscal year is only about half over.

“This restricted program, project and activity or PPA structure, as it’s known, compounds the damage because it restricts our ability to manage where to take reductions in a balanced and rational way,” Clapper said. Thousands of FBI personnel funded out of the intelligence budget could “possibly” be furloughed and over 5,000 contractors will be “let go,” he said.

The required cuts “will reduce human technical and counterintelligence operations, resulting in fewer collection opportunities, while increasing the risk of strategic surprise,” Clapper added. “All we’re asking for is the latitude on how to take them to minimize the damage.”

Senate Intelligence Committee Chairman Dianne Feinstein (D-Calif.) said she was proposing an amendment that would allow intelligence budgets the same degree of flexibility permitted for general Defense Department spending.

Other senators on the panel said they favored giving intelligence agencies more flexibility, but Senate Appropriations Committee Chairman Barbara Mikulski (D-Md.) said she has been barred from attaching such amendments to pending legislation for a continuing resolution on the budget.

“We will not have that in our bill. …We were told both by the House and by others that this was a poison pill,” Mikulski said.

Mikulski pleaded with Clapper and her fellow senators to increase pressure on congressional leaders to address the sequester’s impacts. “I always hope that a higher power will be on my side. … It’s going to take higher power,” she said.